Live chat should be for sale related queries only because it does not take to much time to reply and leave a good impression on the client. On the other hand for technical queries client should be asked to open a support ticket because usually, it takes time to resolve the issue.

That is a waste of the live chat feature and a waste of time for both client and your support reps.
Yes, tickets do take time, mainly because of the wait between each parties responses.
Live chat eliminates this extra time waiting and possibly anxiety. With live chat technical support available, clients are more than happy to wait while their issue is resolved rather than waiting for a ticket that might be misinterpretated 5 times before understood.